Metabolism (from metavallo), the Greek word for "change"), in the most general
sense, is the ingestion and breakdown of complex compounds, coupled with the
liberation of energy, and the consequent generation of waste products. It is a major
process of living organisms, and because this process can happen at many levels
within an organism, we can identify several kinds of metabolism:
When concerning an organism in its entirety, metabolism (also called total
metabolism) is all of the living organism's chemical processes. The organism's
metabolism can be dichotomized into the synthesis of organic molecules (anabolism)
and their breakdown (catabolism).
When concerning a particular substance, metabolism (also called specific metabolism)
is the chemical activity involving this substance in a living organism. This is
commonly the digestion of food, and the disposal of wastes.
When concerning a particular living cell, metabolism (also called cell metabolism)
is all of the chemical processes in that cell.
An abstract definition of metabolism is difficult to make in the same way an
abstract definition of life is difficult to make. For example, according to the
definition above, fire has a metabolism, too (it "eats", for example, wood, converts
it to heat, and disposes ashes), but we would not describe fire as
metabolizing.
Santorio Santorio weighed himself in a chair suspended from a steelyard balance,
before and after a meal, and published the results in Ars de statica medecina, 1614,
the first controlled experiment in human metabolism.
Other subjects related to metabolism are: Aerobic Metabolism, Atkins Diet,
Carbohydrate Metabolism, Detox, Diabetes, Diet, Cholesterol Metabolism, Estrogen
Metabolism, Nutrition and Metabolism, Obesity, Sugar Metabolism, Weight Loss, and
Ways to increase Metabolism.
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